Conventionally, fabricated semiconductor packages are required to be performed with various functional tests, such as direct current test, burn-in test, room/cold test, hot sort test, etc; these tests are used to test functionality of the semiconductor packages, for selecting good-quality packages and eliminating inferior products, thereby assuring yield of package fabrication. The direct current test is to detect the occurrence of electrical failure in assembly of semiconductor packages. The burn-in test allows semiconductor packages to undergo extreme environmental conditions such as high temperature, so as to determine if early failure would occur in practical operation of the semiconductor packages. During the room/cold test, semiconductor packages are treated with room temperate (about 25° C.) or low temperature (about 0° C.), for testing functional impairment of the semiconductor packages. The hot sort test is performed under a high temperature environment of around 80° C., so as to examine electricity or functionality and determine operational speed of semiconductor packages. Since the above functional tests are all conventional in the art, they are not to be further described herein.
For performing the foregoing tests, semiconductor packages need to be electrically connected by a test fixture to a test device e.g. an oven where various temperature or electricity conditions for package testing are conducted. FIGS. 1A and 1B illustrate a conventional test fixture 1, which is used to accommodate BGA (ball grid array) semiconductor packages 10 and electrically connect the semiconductor packages 10 to a test device (not shown) for performing functional tests. As shown in the drawings, the test fixture 1 comprises a circuit board 11 and a plurality of sockets 12 coupled to the circuit board 11. Each socket 12 is a multi-layer structure (normally eight layers), and formed with a fixed-sized through hole 13, allowing the semiconductor package 10 to be received in the through hole 13. Conventionally, about 150 to 300 sockets 12 are mounted on the circuit board 11, and thus, the test fixture 1 can simultaneously accommodate around 150 to 300 semiconductor packages 10 that are intended to undergo functional tests. When the sockets 12 accompanied with the semiconductor packages 10 are disposed on the circuit board 11, the semiconductor packages 10 are allowed to be electrically connected via solder balls 14 to contact terminals 15 formed on the circuit board 11. Then, the circuit board 11 can be coupled to the test device, by which the semiconductor packages 10 are electrically connected to the test device where multiple tests are performed for testing functionality of the semiconductor packages 10. For coupling the circuit board 11 to the test device, for example, the test device can be formed with a socket that is engaged with an input/output (I/O) terminal 16 of the circuit board 11; since this coupling technology is conventional in the art, no further description thereto is to be here detailed.
However, the above conventional test fixture has significant drawbacks. First, a socket used for accommodating a semiconductor package therein is structured with multiple layers, and fabricated by costly and complex processes. And, the socket is formed with a fixed-sized through hole for receiving the semiconductor package; therefore, multiple types of sockets formed with through holes of different dimensions are necessarily fabricated for use with variously sized semiconductor packages. With around 150 to 300 sockets being utilized for each test fixture, it needs to manufacture a plenty of expensive and complicated sockets, and thus greatly increases fabrication costs and process complexity for the test fixture. Moreover, in response to profile miniaturization of semiconductor packages, old sockets designed for use with large packages are out of date and probably have to be discarded, farther making fabrication costs and material waste undesirably increased.
Therefore, how to develop a test fixture applicable for variously sized semiconductor packages, and to allow the test fixture to be cost-effectively fabricated by simplified processes, is a critical subject to investigate herein.